What is the recommended treatment for Immunoglobulin G (IgG) deficiency?

Treatment for Immunoglobulin G (IgG) Deficiency

Immunoglobulin replacement therapy is the standard of care for IgG deficiency, with dosing typically starting at 400-600 mg/kg every 3-4 weeks for intravenous administration or equivalent for subcutaneous administration, adjusted based on clinical response and IgG trough levels. 1, 2

Diagnosis Confirmation Before Treatment

• Confirm diagnosis with repeated measurements of serum IgG levels below age-specific normal range 3
• Evaluate specific antibody production by measuring responses to pneumococcal vaccines before initiating treatment 1, 3
• Assess functional antibody responses rather than just antibody concentration, ideally using opsonophagocytic assays that measure killing of organisms 1
• Document clinical history of recurrent infections, particularly with encapsulated organisms like Streptococcus pneumoniae 1

Treatment Options

Immunoglobulin Replacement Therapy

• Intravenous immunoglobulin (IVIG):

  • Initial dosing: 400-600 mg/kg every 3-4 weeks 1, 4
  • Dose may be increased to 800 mg/kg or higher monthly if needed to keep patient infection-free 1
  • Results in higher peak and lower trough levels between infusions 5

• Subcutaneous immunoglobulin (SCIG):

  • Weekly administration with more stable IgG levels 5, 6
  • May require higher cumulative monthly doses due to lower bioavailability 5
  • Associated with fewer systemic adverse effects but more local reactions 7, 5

• Hyaluronidase-facilitated SCIG:

  • Allows for less frequent administration (every 3-4 weeks) 5
  • Intermediate pharmacokinetic profile between IVIG and conventional SCIG 5

Antimicrobial Therapy

• Consider prophylactic antibiotics for patients with recurrent respiratory infections 1, 3
• Options include:
  • Amoxicillin: 500-1000 mg daily or twice daily for adults 1
  • Trimethoprim/sulfamethoxazole: 160 mg daily or twice daily for adults 1
  • Azithromycin: 500 mg weekly or 250 mg every other day for adults 1

Monitoring During Treatment

• Regular monitoring of IgG trough levels at least every 6-12 months 1, 2
• Monitor blood cell counts and serum chemistry 1
• Adjust dosing based on:
  • Clinical response (infection frequency and severity) 1, 2
  • Growth or weight changes 1
  • Presence of protein loss (e.g., enteric loss) 1
  • Individual variations in IgG catabolism 1

Special Considerations

• IgA deficiency is not a contraindication to IgG therapy, though very rare anaphylactic reactions have been reported 1
• Permanent central venous access solely for IVIG administration should be discouraged due to infection risk 1
• Early treatment helps prevent permanent organ damage such as bronchiectasis 3
• Different patients catabolize administered immunoglobulin at different rates, requiring individualized dosing 1

Adverse Effects Management

• IVIG-related adverse effects:

  • Immediate reactions (within 6 hours): headache, fever, chills (common but usually mild) 7
  • Delayed reactions (6 hours to 1 week): persistent headache, aseptic meningitis, renal failure (less common) 7
  • Rare but serious: thromboembolism and hemolytic reactions 7, 5

• SCIG-related adverse effects:

  • Local reactions: pain, swelling, erythema at injection sites (common but usually mild) 7, 5
  • Systemic reactions: rare compared to IVIG 7

Treatment Efficacy

• The efficacy of IgG replacement for reducing serious bacterial infections in patients with antibody deficiency is well documented 1
• Higher trough levels (above 400-500 mg/dL) are associated with fewer infections 2
• Both IVIG and SCIG have been demonstrated to provide protection from infections and improve health-related quality of life 8